Sheet metal trimming machine



Sept. 12, 1950 w. o. HARTUP 2,521,975

SHEET METAL TRIMMING MACHINE Filed Nov. 15, 194e 2 sheets-sheet 1 IN V EN TOR.

Sept. l2, 1950 w. o. HARTUP SHEET METAL TRIMMING MACHINE 2 Sheets-Sheet 2 Filed Nov. 15, 194e Patented Sept. 12, 1950 UNITED STATES PATENT OFFICE 9 Claims.

This invention relates to a machine for operating upon sheet-metal stampings, especially for trimming the walls of drawn parts.

It is my general object to produce a machine for this purpose which will be self contained, simple in construction and operation, and eincient in performing its work.

Many sheet-metal parts, after being drawn or formed to their desired shape, then have their walls trimmed to provide edges of a desired contour, which may be a continuous edge in a fiat or curved plane, or may include notches or upstanding tabs. Supplementary cutting and forming operations may also be done at or adjacent the trimmed edge, by providing the trimming dies with suitable parts for this purpose.

It is now common practice to do this work in a press, by means of a special die mechanism which carries a pair of trimming dies vertically past cams which cause relative horizontal movement between the dies. Such special mechanism is relatively expensive, and requires the time and use of a still more expensive press. The system is inherently inefficient, in that it utilizes an expensive press designed to work in a vertical direction, to perform an operation in which the requirements for vertical work are substantially only to hold parts in relative position, and in which the productive operations are performed by horizontal movement of parts. Moreover, in such a system, productive work can be done onli7 during one stroke of the press, and an idle return stroke is unavoidable.

In providing a self contained machine it isin part my object to avoid the necessity of using the time of a highly expensive press. It is my further object to provide a machine which will be productive on each stroke, without an idle return stroke, which will lend itself to automatic feeding, which will effectively break the trim scrap to make it easily removable, which will require a minimum of power, and which will be sufficiently simple in construction that' it will be not substantially more expensive than the special mechanism now used in the even more expensive presses.

In carrying out my invention, I mount a laterally movable die plate upon a table, mount one die of a pair of trimming dies on that plate, and provide the table with van upper-die holder which is independently movable to position a complementary die in Working relationship with the die upon the plate and to raise that complementary die to provide clearance for loading and unloading the work on a work holder associated with the lower die. This portion of the structure is similar to that described and claimed in my copending application Serial No. 709,055, led November 9, 1946.

ln accordance with the invention of this application the die plate is mounted on an underlying thrust plate which is provided with inner vertical thrust-receiving faces perpendicular to radii of the die plate, and each of such thrust faces is engaged by a shoe which is in operative engagement with the toe of a bell-crank lever. The several bell-crank levers are pivotally mounted beneath the table and are operated by a cam movable beneath the table.

Preferably, there are four levers and shoes, and four thrust-receiving faces; the levers are arranged in pairs with the levers of each pair operable outwardly in diametrically opposite directions and with the two pairs on diameters perpendicular to each other; and the thrustreceiving faces are in corresponding pairs respectively positioned perpendicular to the thrustlines of the four levers. The levers are desirably lifted by cam-bars slidable horizontally beneath them in a direction atan angle to the vertical planes of lever movement. Two cam-bars may be used, which may be on a single carrier, and each cam bar may operate two of the four levers.

The cam elements selectively raise and`lwer the levers to cause translation of the die plate rst in opposite directions in line with one pair of levers and then in opposite directions in line with the other pair of levers. During each movement of each pair of levers, the other pair is held stationary so that its shoes bear against their associated thrust faces as guides to limit the motion of the die plate to linear motion in the direction of such thrust faces. The cam plate is movable by any suitable power means, conveniently a fluid-operated cylinder, and produces a productive motion of the die plate on each stroke.

The accompanying drawings illustrate my invention. In such drawings, Fig. l is a front elevation of a machine embodying my invention; Fig. 2 is a plan of the machine shown in Fig. 1 on the line 2-2 of Fig. 1; Fig. 3 is a vertical section taken on thelvertical axis of the dies; Fig. 4 is a horizontal section taken on the line 4--4 of Fig. 3, with parts broken away; Fig. 5 is an isometric view of the cam bars and carrier; Fig. 6 is a vertical section in the plane of one of the bell-crank levers; and Fig. '7 is a fragmental isometric view of the heel of one of the bell-crank levers.

The machine shown in the drawing comprises a table l upon which is mounted a frame Il which supports four vertical guide posts l2 at its corners. A die plate I4 is mounted on the table l0 within the frame Il, by means of an underlying thrust plate l5, and the die plate and thrust plate assembly are held on the table by a flange I6 which projects beneath the inner edge of the frame il. The die plate i4 is thus held in slidable relation on the table l] and is permitted limited sliding motion thereover.

An upper die carrier 2t is mounted for vertical movement on the guide posts I2 and is connected by draw bars 2| to a lower cross head 22. A power cylinder 23 is connected between thislower cross head 22 and a frame member 24 So that operation of the power cylinder 23- will raise and lower the upper die carrier 2li. Stop members 25 may :be mounted on the carrier 20 to engage the upper face of the table l0, to limit downward movement of the carrier 2Q.

lThe inner die 3i? of.y a pair of trimming dies is mounted on the die plate i4, and the outer die 3l is mounted on the carrier 20, so that the outer die 3l may be brought down over a work piece 32A into shearing relationshipwith the inner die 30, where sliding movement of the die plate i4 across the table Ill will causethe lower die 3@ to trim the depending edges of the work piece 32.

4The lower die 30 is mounted on the die plate I4l in any suitable manner, as by screws as shown. The die plate I4, the thrust plate l; and the lower die 3o are all provided with aligned openings through which a lower work holder 34 is suppoited on the table lll.v With the relatively small die shown, the openings are conveniently central, and the support comprises a single central post 33. The lower work-holder Sii is shaped to conform to the inside of the Work piece 32, and may slidably engage the top surface of' the lower die 35.

The upper die 3l is mounted on the carrier 2G by means of a supporting ring 35. The upper die 3| has -a central opening which closely lits the outside of the work piece 32, and the support'- ing ring 35 has a similar opening, to receive an upper work holder 36. Conveniently, the opening inthe ring 35-is somewhat larger than that in the die 3l so that the die 3l forms a shoulder within the opening. The work holder 36 is vertically movable within the die 3l and ring 35; and a collar 31 on the work holder 35i engages the shoulder formed by the die 3l, to retain the holder 35.

The parts are so proportioned'that as thetwo dies 3U and 3l are brought together, the holders 3Q and 36 closely embrace the -work piece 32 to hold it in proper position for trimming. After the trimming operation, and when the dies are separated, means is provided to force the upper work holder 36 downwardly with respect tothe die 3|, to eject the workpiece 32 from that die 3i. Conveniently, this is accomplished by providing a knock out bar 38 on top of the dieholder 36, which projects upwardly beyond the carrier 20. A cross member 39 is positioned above the knock out bar 38 to stop the knock out bar during upward travel ofthe carrier 20, andthus hold the upper work holder 33'stationary during the latter part of the upward travel of the carrier 2U.

ln the trimming operation, the die plate. I4 is moved successively in a sequence ofshort strokes in different radial directions across tl-ie table l5 and is then returned to centenby cam means movable below the table it. For this purpose, the thrust plate l5, which supports the die plate I4, is provided with four generally square open` ings @il to 43, arranged in pairs with the openings of each pair diametrically opposite each other, and with the pairs at right angles to each other. Thus, as shown in Figs. 3 and 4, the pair of openings ll land l lie opposite to each other on the 45 diameter extending diagonally from the right front of the machine to the left rear, and the pair of openings 42 and 43 lie opposite to each other on the 45 diameter extending diagonally from the left front to the right rear.

The radially outward walls of the square openings Ll to 43 form thrust-receiving faces i4-M which are respectively perpendicular to radii from the center of the die plate M, and are at right'angles to each other. Each such face also serves as a guide during movements of the die plate parallel thereto. The faces fili-47 are respectivelyengaged by U-shaped shoes Eil-53, which present broad surfaces in engagement therewith but which are shorter than such faces 413-47, to permit relative sliding longitudinal of the faces lll-31. Y

Bell-crank levers 54-51 are pivotally mounted below the table on horizontal axes respectively parallel to the thrust faces lid-57. Each bell crank lever 541-51 extends through an opening in the table l and has a toe embraced within one of the shoes 55-53, soy that upward pivotal movement of a lever moves its associated shoe horizontally and radially outward against the opposing thrust-receiving face 614-41 ofthe thrust plate l5. Eachlever has a heelwhich moves generally vertically during pivotal movement of the lever, andthe lever heels are in operative engagement with cambars 6d and 65 on a` cam carrier 6B, which is slidable longitudinally below the table IU.

The cam carrier 50 is slidably mounted on a horizontal support 6|, which may be the upper surface of the frame member 29', rigid with the frame of the table l, and is guided across such support 6l by longitudinal rails 52 slidably received in grooves in the longitudinal` edges of the carrier 65. Sliding movement of the cam may be powered in any convenient way, conveniently by connecting it directly to the piston of a fluid operated cylinder ll mounted below the table Ill` The four levers i4-51 are pivotally movable in two vertical planes at right angles to each other and at 45 with the center line of movement of the cam 5t.. In thisarrangement, the levers are all equidistant from the center line of cam movement, andone lever ofy each pair of opposite levers lies on each side of such center line. The heels of the two levers` 54-and- 55, on the back side of such center line, ride on the-cam-bar 64 mounted along the longitudinal back edge of the cam carrier 6G, and the heels of the two levers 55 and 51 ride on thel cam bar S5 along the front edge of the carrier Ell. As may be seenin Fig. 5,.tl"1e cam bar 513- includes along flat section 66 at itsforward` (left)v end, thenalow 5l, thena rise 38, and then another. long flat section S9 at the other end of theY bar 615. The cam bar 65' includes a short flat section lil, a rise TI, a` low l2, a central flatsectionflS, then arise '14', a low 15, and a short flat end section TS. Conveniently, the faces are flat transversely. As shown in Fig. 7, the heels of the levers 54--57 extend transversely ofthe cam bars and hence diagonally with' respect to the levers and to-take account of vthe relatively oblique movement of the levers, their heels are desirably roundedin planes transverse to the cam faces.

With the cam carrier 63 at the right-hand end of its stroke, as shown in Figs. 4 and 5 the heels of the cams 54-51 engage the cam bars 64 and 65 as indicated in Fig. 5, and movement of the cam through a stroke to the left operates the levers as follows:

First, the right rear lever 56 enters the low 61 and the left front lever 51 engages the rise 1I. This raises the lever 51 to exert horizontal thrust on its shoes 53, while the cam 56 is lowered to permit the shoe 52 to retract, and the die plate I4 is moved diagonally forward and to the left. Meanwhile, the other pair of diametrically opposite levers 54 and 55 ride respectively on the flats 56 and 13 of the two cam bars, and hold their shoes 5D and 5| stationary to engage the faces 44 andL 45 as guides, to limit the cam plate to linear movement parallel with the faces 44 and 45 and in the direction of the pair of levers 55 and 51. The lever 56 then engages the rise 68 while the lever 51 enters the low 12, which causes movev ment of the die plate in the opposite direction from its rst movement, the levers 54 and 55 being still in engagement with the flats 66 and 13 so that their associated shoes guide the plate I4 for linear movement in that direction. The levers 56 and 51 which have moved now reach the flats 69 and 13, and the cam plate I4 is centered.

The left-rear lever 54 then enters the low 61 and the right front lever 55 engages the rise 14, to produce a movement of the die plate diagonally forward and to the right in the direction of the lever 55. Meanwhile, the levers 56 and 51 ride respectively on the ats 69 and 13 to hold their associated shoes stationary as guides for that movement. The levers 54 and 55 are then engaged by the cam elements 68 and 15 to cause a reverse movementof the plate I4 in the opposite direction. The levers 54 and 55 then finally reach the flats 69 and 16, and the die plate I4 is again entered.

The resulting movement of the die plate Ill is thus rst successively in diametrically opposite directions along the diagonal thrust line of the levers 54 and 55. It is then centered, and is then movedsuccessively in diametrically oposite directions along the diagonal thrust line of the levers 56 and 51 at right angles to the first movements.

Such sequence of die plate movements completes a full trimming cycle. Movement of the die carrier 63 in the reverse direction will likewise produce a similar sequence of movements of the die Plate I4 for another full trimming cycle, but in the reverse order from that of the rst stroke.

The cam carrier 63 may be reciprocated through its stroke by any desired source of power, conveniently a fluid operated cylinder 11.

O-peration of the machine is as follows:

The upper die carrier is assumed to be in raised position, as shown in full lines in Fig. l, so that the dies are open. A sheet metal stamping or work piece 32 is placed on the lower work holder 34 in proper relative position over the lower die 3U. The power cylinder 23 is then operated to lower the upper-die carrier 26 to bring the upper die 3| downward toward shearing relationship with the lower die 36 and to bring the upper work-holder 36 into engagement with the upper surface of the work. This downward movement is stopped by engagement of the stop members 25 with the upper face of the table I D, when the dies are in proper operative relation.

The power cylinder 11 is now` operated to move the cam carrier 63 through a full stroke. 'Ihis causes successive radial movements of the die plate I4 across the table lil, as set forth above, to carry the lower die 30 through similar movements with respect to the stationary upper die 3 I. Such movements are rst oppositely in the direction of one diagonal diameter of the die plate I 4, then to center, then oppositely in the direction of the diagonal diameter at right angles with the first, and the plate I4 and die 30 are then returned to a centered position. This completes a full sequence of trimming operations. The upper die is now raised, by operation of the power cylinder 23. As the upper die 3| rises, the work 32 will normally remain within it and be carried upward with it. As the die carrier 2] approaches the upper limit of its travel, the knock-out bar 38 will engage the xed cross member 39, and will stop further vertical movement of the upper work holder 35. Continued upward movement of the carrier 26 will carry the die 3l] away from the work 32, and permit that work to drop out of the die 3|.

The machine is now reloaded with another work piece 32, the power cylinder 33 operated to lower the upper die 3l, and the power cylinder 11 operated to move the cam carrier 63 through a stroke in the opposite direction. Such opposite stroke produces a full productive sequence of radial movements of the lower die, in a reverse order from that occurring during the forward stroke.

The machine may be loaded and unloaded manually, and its two power cylinders 23 and 11 may be operated by manual controls. But the machine readily adapts itself to automatic loading and unloading, and whether the loading operations are manual or automatic, the power cylinders 23 and 11 may be operated by interlocking or automatic controls. Such cylinders may be operated hydraulically, or conveniently by compressed air, and may be replaced with other power mechanism as desired. The dies 30 and SI are readily interchangeable with other pairs of dies, to trim a wide variety of stampings. Such dies may be either smaller than those shown, or may be larger, up to the limit of the area of the die plate. As desired, the die plate I4 itself may readily be removed, and without disturbing other operative parts of the machine'. The dies used in the machine may be trimming dies, or dies which both trim and slit or punch edge portions of the work, and any such dies may be provided with means to do minor forming operations on the work, in accordance with known practice, but with substantially greater liberty than in prior machines. The machine is inherently quiet and smooth in operation, so that its parts and dies used with it are subjected to minimum wear.

I claim as my invention:

l. A machine for operating upon the walls of sheet-metal stampings, comprising a die-plate movable in its plane, a complementary die holder, a plurality of thrust-receiving faces normal to said die-plate and to radii from its center, a plurality of levers pivoted to move in planes containing said radii and normal to the plane of the die plate, said levers being in thrust-transmitting relation with said thrust-receiving faces, and cam means movable beneath said die plate for selective operation of said levers to thrust said die plate successively in radial directions.

2. A machine for operating upon the walls of sheet-metal stampings, comprising a die-plate acercas ,i movable nits plane, a complementary'die holder, a plurality of thrust-receiving faces normalv to said die-plate and to radii from its center, a plurality of levers pivoted to move in planes containing said radii and normal to the plane of the die plate, said levers being in thrust-transmitting relation with said thrust-receiving faces,- and cam means movable beneath said die plate for selective operation of said levers to thrust said die plate successively in radial directions, said cam means being arranged so that during its thrust movement of one lever it causes other levers to guide said die plate for movement in the direction of thrust movement.

3. A machine for operating upon the walls of sheet-metal stampings, comprising a die-plate movable in its plane, a complementary die holder, a plurality of thrust-receiving faces normal to said die-plate and to radii from its center, a plurality of levers pivoted to move in planes containing said radii and normal to the plane of the die plate, said levers being in thrust-transmitting relation with said thrust-receiving faces, and cam means movable beneath said die plate for selective operation of said levers to thrust said die plate successively in radial directions, said levers being arranged in diametrically opposite pairs with the plane of each pair at right angles to the plane of another pair, said cam means being arranged so that during the movements of one pair of levers it holds the right-angle pair stationary in guiding relation with respect to its associated thrust receiving faces.

4. A machine for operating upon the walls of sheet-metal stampings, comprising a die-plate movable in its plane, two pairs of parallel thrustreceiving faces normal to said die plate and to planesat right angles to each other and to said die plate, two pairs of levers pivoted below said die plate to move in said planes against said thrust-receiving faces, and cam means to operate successively each pair of levers and simultaneously to hold the other pair stationary in guiding relationship with respect to its associated thrust-receiving faces.

5. The machine as dened in claim 1 in which the levers have toes movable generally horizontally against their thrust-receiving faces, and heels which move generally vertically, and in which the cam means isl slidable parallel beneaththe die plate in working relation withthe heels of' said levers.

6. The machine as defined invclaim 4` in which the levers have toes movable generally horizontally against their thrust-receiving faces, and heels which move generally vertically, and in which the cam means is slidable parallel beneath the die plate in working relation with the heels of said levers.

'i'. The machine as defined* in claim 4, in which the cam means are slidable parallel beneath the diefplate'and the planes of said'levers'are` at 45 with the center line of cam movement, said cam means comprising a pair of cam bars each of which engages twol of said levers.

8. A machine for operating upon the walls of sheet-metal stampings, comprising a die plate adapted to support a trimming die and movable in its plane, a complementary die holder, a plurality of levers pivoted beneath said die plate in operative relation therewith, and cam meansfbeneath said die plate in operative relation with said levers and operable to move said levers to 5 cause successive radial movements of said die plate in its plane.

9. A machine for operating upon the walls of sheet-metal stampings, comprising a die plate adapted to support a trimming die and movable in its plane, a complementary die holder, a plurality of levers pivoted beneath said die plate in operative relation therewith, and cam means beneath said die' plate in operative relation with said levers and operable to move said levers to cause successive radial movements of said dieplate in its plane, said-levers being displaced from the axis of the die position on said plate, and a stationary work-holder support on said axis.

WM. O. HARTUP.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,125,259 Buff Aug. 2, 1938 2,3.20g272 Friden May 25, 1943" 

